If you plan on covering systems besides the Turbo (just a thought), here's some picks (all are available on romhacking.net):
-NES-
Adventure Island 4 (Translation) - The Adventure Island sequel that never made it to America, which funnily enough, takes a page from the Wonderboy sequels.
Battle Kid (Homebrew) - In my opinion, the best homebrew on the NES, and from what I've played, the only one that feels like a legit game for the system.
Castlevania: Chorus of Mysteries (Castlevania 1 Hack) - One of the better Castlevania 1 hacks. It actually feels like a brand new game once you get past the first level.
Downtown Special (Translation) - River City Ransom's sequel that was never released overseas!
Extra Mario Bros. (SMB1 Hack) - Super Mario Bros 1 meets Metroid. Seriously.
Fire Emblem 1 (Translation) - It is what it says...
Mario Adventure (SMB3 Hack) - This is often considered the best hack of Super Mario Bros. 3.
The Portopia Serial Murder Case (Translation) - The famous (in Japan) adventure game made by Yuji Horii, before he made the even more famous (worldwide) Dragon Quest.
Silva Saga (Translation) - An RPG that's supposed to be pretty good.
Sweet Home (Translation) - A Survival Horror/RPG by Capcom that was the inspiration for Resident Evil.
Zelda Challenge: Outlands (Zelda 1 Hack) - One of the better Zelda 1 hacks, but very difficult.
-SNES-
Oh No! More Zombies Ate my Neighbors! (ZAMN Hack) - A well done fan-made semi-sequel to ZAMN.
Shin Megami Tensei (Translation) - A very sweet RPG where you recruit demons to join your party. Contains multiple endings. BE ABSOLUTELY SURE that you play the bug-fixed version.
Shodai Nekketsu Kouha Kunio-kun (Translation) - Another sequel to River City Ransom that was never released overseas.
Starfox 2 (Translation) - The rumors are true!
-Genesis-
Gleylancer (Translation) - A shooter! With a STORY!
Langrisser 2 (Translation) - A Strategy RPG. The first in the series was released here as Warsong.
Sonic 1 Megamix (Sonic 1 Hack) - This is supposed to be quite excellent.
Streets of Rage 3 (Translation) - A translation of the Japanese version. Includes story and difficulty balancing that was cut out of the American version.